1. Field of the Invention
The present invention relates to a purple martin birdhouse which provides correct polarization of the birdhouse on a non-rotatable telescoping pole. The birdhouse is mounted to the pole by a receiver and the pole is formed from a plurality of sections, the receiver and the sections of the pole having a bore of cross section the shape of a convex polygon.
2. Brief Description of the Prior Art
Purple martins have become dependent on humans for supplying them with nesting sites. It is a mutually beneficial relationship as a single purple martin can eat up to 2,000 mosquitoes and other insects a day. Purple martins are aerial insectivores, meaning that they catch all of their food in flight. In addition to being efficient and effective destroyers of insects, there are other good reasons for humans to cultivate the relationship. Purple martins are beautiful, graceful birds to watch. They begin singing early in the morning and are entertaining to watch. The birds are like calendars, marking the seasons, since every phase of their annual cycle (from arrival, territory establishment, nest-building, egg-laying, hatching, fledgling and departure) is done on a regular and predictable schedule.
Purple martins are a gregarious species and prefer to nest in multi-compartmentalized birdhouses. A purple martin birdhouse must be managed to reduce parasite infections and guarded against European starlings and English house sparrows which will otherwise out-compete the martins for the nesting compartments. An unmanaged purple martin colony is one that is at high risk of being lost from one year to the next.
To facilitate the effective management of the colony, the birdhouse should be checked periodically and used martin nests and the nests of other species removed. Since a purple martin birdhouse is optimally placed at a height of 12-15 feet, the birdhouse should be on a telescoping pole that allows the house to be lowered vertically without disturbing any eggs. Lowering the house will not disturb the martins while they are nesting. They will fly away initially, but they will quickly return once the house is back up. Caution must be used, however, not to disturb the birdhouse if some of the babies are about to fledge as they may be scared into flying too soon.
When a birdhouse is lowered for a nest check, it is essential that it have the same polarization when it is returned since martins recognize their own nest compartment by its height, relative position and compass direction. If a birdhouse is repositioned in a different compass direction, havoc will break out. Purple martins will go into the compartment in the position that was their own and perhaps find nestlings, when all they had was eggs. In such case, they may throw the foreign young out. Others, while looking for their nests will trespass into the compartments of others, resulting in prolonged and potentially lethal battles. The end result can be reproductive failure, leading to colony-site abandonment.
A purple martin birdhouse should be taken down and cleaned out at the end of the season. If a person makes the mistake of leaving the martin house out, and open, over the winter and paper wasps, squirrels, American kestrels or screech owls take up residence before the martins return from migration, the martins will abandon the house. When the birdhouse is put back up, at the beginning of a season, it is important that it be reinstalled in the same compass direction as last year, otherwise there will be the same kind of strife between the returning pairs of birds that occurs if the house is reoriented during a nest check.
There are telescoping poles for mounting a purple martin birdhouse, most, however, have sections that permit the rotation of the telescoping members or that permit the rotation of the house, either during a nest check or during reinstallation of the house at the beginning of the season. To avoid problems, a person must be careful to mark the sections and the house to be certain that the house maintains the correct polarization. People either forget to mark the sections and the house or forget, between uses, what the markings mean. There are non-rotating telescoping poles proposed for use with purple martin birdhouses that make use of elaborate and complicated mechanisms to prevent rotation of the sections or the house. Such means usually include elongate guide means on the sections and additional components with stationary guiding structure which do not form part of the telescoping members, e.g., U.S. Pat. No. 3,792,685 to Wiener. Such poles are costly to fabricate and are lacking in structural strength.